Most recent electronic devices include various elements mounted on a printed circuit board. Since the elements are sensitive to electromagnetic wave interference (EMI) generated by internal interference sources or external interference sources, malfunction of the electronic devices may occur due to electromagnetic waves.
An electromagnetic wave is a phenomenon of moving energy that includes an electric field and a magnetic field moving together in the form of sine waves. The electromagnetic wave is useful for an electronic device such as a wireless communication device or a radar but causes malfunction of electronic and communication devices and also has harmful effects on the human body.
The electric field is generated by a voltage and easily shielded when far away or by obstacles such as wood. However, the magnetic field is generated by a current and is inverse proportional to a distance and has a property of not being easily shielded. Accordingly, in an electronic device, electronic components such as elements mounted on a printed circuit board are covered by a shield-can formed of a metal to shield EMI generated by an interference source. Therefore, malfunction of the electronic device itself may be prevented and other electronic devices which are nearby may be prevented from being affected.
In general, sidewalls, in which upper and lower sides are open, and an upper plate may be separately manufactured in order to make the shield-can, and the shield-can is typically mounted on the printed circuit board using a method in which the upper plate is assembled on the upper portions of the sidewalls.
Meanwhile, the upper plate needs to have a sufficient thickness to completely fill a space between the shield-can and a metal bracket according to specifications of a product. However, in a case in which an overall thickness of the upper plate formed of a metal material is simply increased, a vertical resistance is increased, and thus there is a problem of degrading EMI shielding performance.